Honestly I am willing to allow all xenos except dark eldar, because dark eldar mechanics require torture that would not fit in this game. But having said that I would much prefer human characters as it is a pain to work out how xenos would join the group. So if you're going to go that route make sure your character is well written and has a good reason to be allowed on a rogue trader vessel.

second question: would you mind tweaking the rules a bit to allow one of the more accepted and stable strains of Abhumans (such as a Felinind mysteriously far from home or a surviving Squat just trying to make his way). I'd be willing to work with you to modify an appropriate home world or to create a Lineage

also (after looking over your PCs to make sure nothing I'm thinking up has "too much overlap") are you sure you need a pilot? the Void-Masters that appear to be in your game isn't a gunner, they appear to possess Mastery of Space and are very good pilots. It just sounds to me like you're looking for more of the same. or am I wrong?